1 // Copyright 2014 PDFium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
6
7 #include "core/fxcodec/jbig2/JBig2_ArithDecoder.h"
8
9 #include "core/fxcodec/jbig2/JBig2_BitStream.h"
10 #include "core/fxcrt/fx_memory.h"
11
12 namespace {
13
14 const JBig2ArithCtx::JBig2ArithQe kQeTable[] = {
15 // Stupid hack to keep clang-format from reformatting this badly.
16 {0x5601, 1, 1, true}, {0x3401, 2, 6, false}, {0x1801, 3, 9, false},
17 {0x0AC1, 4, 12, false}, {0x0521, 5, 29, false}, {0x0221, 38, 33, false},
18 {0x5601, 7, 6, true}, {0x5401, 8, 14, false}, {0x4801, 9, 14, false},
19 {0x3801, 10, 14, false}, {0x3001, 11, 17, false}, {0x2401, 12, 18, false},
20 {0x1C01, 13, 20, false}, {0x1601, 29, 21, false}, {0x5601, 15, 14, true},
21 {0x5401, 16, 14, false}, {0x5101, 17, 15, false}, {0x4801, 18, 16, false},
22 {0x3801, 19, 17, false}, {0x3401, 20, 18, false}, {0x3001, 21, 19, false},
23 {0x2801, 22, 19, false}, {0x2401, 23, 20, false}, {0x2201, 24, 21, false},
24 {0x1C01, 25, 22, false}, {0x1801, 26, 23, false}, {0x1601, 27, 24, false},
25 {0x1401, 28, 25, false}, {0x1201, 29, 26, false}, {0x1101, 30, 27, false},
26 {0x0AC1, 31, 28, false}, {0x09C1, 32, 29, false}, {0x08A1, 33, 30, false},
27 {0x0521, 34, 31, false}, {0x0441, 35, 32, false}, {0x02A1, 36, 33, false},
28 {0x0221, 37, 34, false}, {0x0141, 38, 35, false}, {0x0111, 39, 36, false},
29 {0x0085, 40, 37, false}, {0x0049, 41, 38, false}, {0x0025, 42, 39, false},
30 {0x0015, 43, 40, false}, {0x0009, 44, 41, false}, {0x0005, 45, 42, false},
31 {0x0001, 45, 43, false}, {0x5601, 46, 46, false}};
32
33 const unsigned int kDefaultAValue = 0x8000;
34
35 } // namespace
36
37 JBig2ArithCtx::JBig2ArithCtx() = default;
38
DecodeNLPS(const JBig2ArithQe & qe)39 int JBig2ArithCtx::DecodeNLPS(const JBig2ArithQe& qe) {
40 bool D = !m_MPS;
41 if (qe.bSwitch)
42 m_MPS = !m_MPS;
43 m_I = qe.NLPS;
44 ASSERT(m_I < FX_ArraySize(kQeTable));
45 return D;
46 }
47
DecodeNMPS(const JBig2ArithQe & qe)48 int JBig2ArithCtx::DecodeNMPS(const JBig2ArithQe& qe) {
49 m_I = qe.NMPS;
50 ASSERT(m_I < FX_ArraySize(kQeTable));
51 return MPS();
52 }
53
CJBig2_ArithDecoder(CJBig2_BitStream * pStream)54 CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream)
55 : m_pStream(pStream) {
56 m_B = m_pStream->getCurByte_arith();
57 m_C = (m_B ^ 0xff) << 16;
58 BYTEIN();
59 m_C = m_C << 7;
60 m_CT = m_CT - 7;
61 m_A = kDefaultAValue;
62 }
63
~CJBig2_ArithDecoder()64 CJBig2_ArithDecoder::~CJBig2_ArithDecoder() {}
65
Decode(JBig2ArithCtx * pCX)66 int CJBig2_ArithDecoder::Decode(JBig2ArithCtx* pCX) {
67 ASSERT(pCX);
68 ASSERT(pCX->I() < FX_ArraySize(kQeTable));
69
70 const JBig2ArithCtx::JBig2ArithQe& qe = kQeTable[pCX->I()];
71 m_A -= qe.Qe;
72 if ((m_C >> 16) < m_A) {
73 if (m_A & kDefaultAValue)
74 return pCX->MPS();
75
76 const int D = m_A < qe.Qe ? pCX->DecodeNLPS(qe) : pCX->DecodeNMPS(qe);
77 ReadValueA();
78 return D;
79 }
80
81 m_C -= m_A << 16;
82 const int D = m_A < qe.Qe ? pCX->DecodeNMPS(qe) : pCX->DecodeNLPS(qe);
83 m_A = qe.Qe;
84 ReadValueA();
85 return D;
86 }
87
BYTEIN()88 void CJBig2_ArithDecoder::BYTEIN() {
89 if (m_B == 0xff) {
90 unsigned char B1 = m_pStream->getNextByte_arith();
91 if (B1 > 0x8f) {
92 m_CT = 8;
93
94 switch (m_State) {
95 case StreamState::kDataAvailable:
96 // Finished decoding data (see JBIG2 spec, Section E.3.4).
97 m_State = StreamState::kDecodingFinished;
98 break;
99 case StreamState::kDecodingFinished:
100 // Allow one more call in the finished state. https://crbug.com/947622
101 m_State = StreamState::kLooping;
102 break;
103 case StreamState::kLooping:
104 // Looping state detected. Mark decoding as complete to bail out.
105 // https://crbug.com/767156
106 m_Complete = true;
107 break;
108 }
109 } else {
110 m_pStream->incByteIdx();
111 m_B = B1;
112 m_C = m_C + 0xfe00 - (m_B << 9);
113 m_CT = 7;
114 }
115 } else {
116 m_pStream->incByteIdx();
117 m_B = m_pStream->getCurByte_arith();
118 m_C = m_C + 0xff00 - (m_B << 8);
119 m_CT = 8;
120 }
121
122 if (!m_pStream->IsInBounds())
123 m_Complete = true;
124 }
125
ReadValueA()126 void CJBig2_ArithDecoder::ReadValueA() {
127 do {
128 if (m_CT == 0)
129 BYTEIN();
130 m_A <<= 1;
131 m_C <<= 1;
132 --m_CT;
133 } while ((m_A & kDefaultAValue) == 0);
134 }
135